Method for combining transfer functions and predetermined key creation

ABSTRACT

A method for combining transfer functions with predetermined key creation. In one embodiment, digital information, including a digital sample and format information, is protected by identifying and encoding a portion of the format information. Encoded digital information, including the digital sample and the encoded format information, is generated to protect the original digital information. In another embodiment, a digital signal, including digital samples in a file format having an inherent granularity, is protected by creating a predetermined key. The predetermined key is comprised of a transfer function-based mask set to manipulate data at the inherent granularity of the file format of the underlying digitized samples.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/602,777, which is a continuation application of U.S. patentapplication Ser. No. 09/046,627 (which issued Jul. 22, 2003, as U.S.Pat. No. 6,598,162), which is a continuation-in-part of U.S. patentapplication Ser. No. 08/587,943, filed Jan. 17, 1996, (which issued Apr.28, 1998, as U.S. Pat. No. 5,745,943). The entire disclosure of U.S.patent application Ser. No. 09/046,627 (which issued Jul. 22, 2003, asU.S. Pat. No. 6,598,162) and U.S. patent application Ser. No.08/587,943, filed Jan. 17, 1996, (which issued Apr. 28, 1998, as U.S.Pat. No. 5,745,943) are hereby incorporated by reference in theirentireties. This application claims the benefit of U.S. patentapplication Ser. No. 08/587,943, filed Jan. 17, 1996, entitled “Methodfor Stega-Cipher Protection of Computer Code,” (issued as U.S. Pat. No.5,745,569 on Apr. 28, 1998), the entire disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The invention relates to the protection of digital information. Moreparticularly, the invention relates to a method for combining transferfunctions with predetermined key creation.

BACKGROUND OF THE INVENTION

Increasingly, commercially valuable information is being created andstored in “digital” form. For example, music, photographs and video canall be stored and transmitted as a series of numbers, such as 1's and0's. Digital techniques let the original information be recreated in avery accurate manner. Unfortunately, digital techniques also let theinformation be easily copied without the information owner's permission.

Because unauthorized copying is clearly a disincentive to the digitaldistribution of valuable information, it is important to establishresponsibility for copies and derivative copies of such works. Forexample, if each authorized digital copy of a popular song is identifiedwith a unique number, any unauthorized copy of the song would alsocontain the number. This would allow the owner of the information, suchas a song publisher, to investigate who made the unauthorized copy.Unfortunately, it is possible that the unique number could be erased oraltered if it is simply tacked on at the beginning or end of the digitalinformation.

As will be described, known digital “watermark” techniques give creatorsand publishers of digitized multimedia content localized, securedidentification and authentication of that content. In considering thevarious forms of multimedia content, such as “master,” stereo, NationalTelevision Standards Committee (NTSC) video, audio tape or compact disc,tolerance of quality will vary with individuals and affect theunderlying commercial and aesthetic value of the content. For example,if a digital version of a popular song sounds distorted, it will be lessvaluable to users. It is therefore desirable to embed copyright,ownership or purchaser information, or some combination of these andrelated data, into the content in a way that will damage the content ifthe watermark is removed without authorization.

To achieve these goals, digital watermark systems insert ownershipinformation in a way that causes little or no noticeable effects, or“artifacts,” in the underlying content signal. For example, if a digitalwatermark is inserted into a digital version of a song, it is importantthat a listener not be bothered by the slight changes introduced by thewatermark. It is also important for the watermark technique to maximizethe encoding level and “location sensitivity” in the signal to forcedamage to the content signal when removal is attempted. Digitalwatermarks address many of these concerns, and research in the field hasprovided extremely robust and secure implementations.

What has been overlooked in many applications described in the art,however, are systems which closely mimic distribution of content as itoccurs in the real world. For instance, many watermarking systemsrequire the original un-watermarked content signal to enable detectionor decode operations. These include highly publicized efforts by NEC,Digimarc and others. Such techniques are problematic because, in thereal world, original master copies reside in a rights holders vaults andare not readily available to the public.

With much activity overly focused on watermark survivability, thesecurity of a digital watermark is suspect. Any simple linear operationfor encoding information into a signal may be used to erase the embeddedsignal by inverting the process. This is not a difficult task,especially when detection software is a plug-in freely available to thepublic, such as with Digimarc. In general, these systems seek to embedcryptographic information, not cryptographically embed information intotarget media content.

Other methods embed ownership information that is plainly visible in themedia signal, such as the method described in U.S. Pat. No. 5,530,739 toBraudaway et al. The system described in Braudaway protects a digitizedimage by encoding a visible watermark to deter piracy. Such animplementation creates an immediate weakness in securing the embeddedinformation because the watermark is plainly visible. Thus, no searchfor the embedded signal is necessary and the watermark can be moreeasily removed or altered. For example, while certainly useful to somerights owners, simply placing the symbol “.COPYRGT.” in the digitalinformation would only provide limited protection. Removal by adjustingthe brightness of the pixels forming the “.COPYRGT.” would not bedifficult with respect to the computational resources required.

Other relevant prior art includes U.S. Pat. No. 4,979,210 and 5,073,925to Nagata et al., which encodes information by modulating an audiosignal in the amplitude/time domain. The modulations introduced in theNagata process carry a “copy/don't copy” message, which is easily foundand circumvented by one skilled in the art. The granularity of encodingis fixed by the amplitude and frequency modulation limits required tomaintain inaudibility. These limits are relatively low, making itimpractical to encode more information using the Nagata process.

Although U.S. Pat. No. 5,661,018 to Leighton describes a means toprevent collusion attacks in digital watermarks, the disclosed methodmay not actually provide the security described. For-example, in caseswhere the watermarking technique is linear, the “insertion envelope” or“watermarking space” is well-defined and thus susceptible to attacksless sophisticated than collusion by unauthorized parties. Over-encodingat the watermarking encoding level is but one simple attack in suchlinear implementations. Another consideration not made by Leighton isthat commercially-valuable content may already exist in a un-watermarkedform somewhere, easily accessible to potential pirates, gutting the needfor any type of collusive activity. Digitally signing the embeddedsignal with preprocessing of watermark data is more likely to preventsuccessful collusion. Furthermore, a “baseline” watermark as disclosedis quite subjective. It is simply described elsewhere in the art as the“perceptually significant” regions of a signal. Making a watermarkingfunction less linear or inverting the insertion of watermarks would seemto provide the same benefit without the additional work required tocreate a “baseline” watermark. Indeed, watermarking algorithms shouldalready be capable of defining a target insertion envelope or regionwithout additional steps. What is evident is the Leighton patent doesnot allow for initial prevention of attacks on an embedded watermark asthe content is visibly or audibly unchanged.

It is also important that any method for providing security alsofunction with broadcasting media over networks such as the Internet,which is also referred to as “streaming.” Commercial “plug-in” productssuch as RealAudio and RealVideo, as well as applications by vendorsVDONet and Xtreme, are common in such network environments. Most digitalwatermark implementations focus on common file base signals and fail toanticipate the security of streamed signals. It is desirable that anyprotection scheme be able to function with a plug-in player withoutadvanced knowledge of the encoded media stream.

Other technologies focus solely on file-based security. Thesetechnologies illustrate the varying applications for security that mustbe evaluated for different media and distribution environments. Use ofcryptolopes or cryptographic containers, as proposed by IBM in itsCryptolope product, and InterTrust, as described in U.S. Pat. Nos.4,827,508, 4,977,594, 5,050,213 and 5,410,598, may discourage certainforms of piracy. Cryptographic containers, however, require a user tosubscribe to particular decryption software to decrypt data IBM'sInfoMarket and InterTrust's DigiBox, among other implementations,provide a generalized model and need proprietary architecture tofunction. Every user must have a subscription or registration with theparty which encrypts the data. Again, as a form of general encryption,the data is scrambled or encrypted without regard to the media and itsformatting. Finally, control over copyrights or other neighboring rightsis left with the implementing party, in this case, IBM, InterTrust or asimilar provider.

Methods similar to these “trusted systems” exist, and Cerberus CentralLimited and

Liquid Audio, among a number of companies, offer systems which mayfunctionally be thought of as subsets of IBM and InterTrust's moregeneralized security offerings. Both Cerberus and Liquid Audio proposeproprietary player software which is registered to the user and “locked”in a manner parallel to the locking of content that is distributed via acryptographic container. The economic trade-off in this model is thatusers are required to use each respective companies' proprietary playerto play or otherwise manipulate content that is downloaded. If, as isthe case presently, most music or other media is not available via theseproprietary players and more companies propose non-compatible playerformats, the proliferation of players will continue. Cerberus and LiquidAudio also by way of extension of their architectures provide for“near-CD quality” but proprietary compression. This requirement stemsfrom the necessity not to allow content that has near-identical datamake-up to an existing consumer electronic standard, in Cerberus andLiquid Audio's case the so-called Red Book audio CD standard of 16 bit44.1 kHz, so that comparisons with the proprietary file may not yieldhow the player is secured. Knowledge of the player's file format rendersits security ineffective as a file may be replicated and played on anycommon player, not the intended proprietary player of the provider ofpreviously secured and uniquely formatted content. This is the parallelweakness to public key crypto-systems which have gutted security ifenough plain text and cipher text comparisons enable a pirate todetermine the user's private key.

Many approaches to digital watermarking leave detection and decodingcontrol with the implementing party of the digital watermark, not thecreator of the work to be protected. A set of secure digital watermarkimplementations address this fundamental control issue forming the basisof key-based approaches. These are covered by the following patents andpending applications, the entire disclosures of which are herebyincorporated by reference: U.S. Pat. No. 5,613,004 entitled“Steganographic Method and Device” and its derivative U.S. patentapplication Ser. No. 08/775,216 (issued as U.S. Pat. No. 5,687,236 onNov. 11, 1997), U.S. patent application Ser. No. 08/587,944 entitled“Human Assisted Random Key Generation and Application for DigitalWatermark System,” (issued as U.S. Pat. No. 5,822,432 on Oct. 13, 1998)U.S. patent application Ser. No. 08/587,943 entitled “Method forStega-Cipher Protection of Computer Code,” (issued as U.S. Pat. No.5,745,569 on Apr. 28, 1998) U.S. patent application Ser. No. 08/677,435entitled “Optimization Methods for the Insertion, Protection, andDetection of Digital Watermarks in Digitized Data,” (issued as U.S. Pat.No. 5,889,868 on Jul. 2, 1996) and U.S. patent application Ser. No.08/772,222 entitled “Z-Transform Implementation of Digital Watermarks”(issued as U.S. Pat. No. 6,078,664 on Jun. 20, 2000). Public keycrypto-systems are described in U.S. Pat. Nos. 4,200,770, 4,218,582,4,405,829 and 4,424,414, the entire disclosures of which are also herebyincorporated by reference.

In particular, an improved protection scheme is described in “Method forStega-Cipher Protection of Computer Code,” U.S. patent application Ser.No. 08/587,943 (issued as U.S. Pat. No. 5,745,569 on Apr. 28, 1998).This technique uses the key-based insertion of binary executablecomputer code within a content signal that is subsequently, andnecessarily, used to play or otherwise manipulate the signal in which itis encoded. With this system, however, certain computationalrequirements, such as one digital player per digital copy of content,may be necessitated. For instance, a consumer may download many copiesof watermarked content. With this technique, the user would also bedownloading as many copies of the digital player program. While thisform of security may be desirable for some applications, it is notappropriate in many circumstances.

Finally, even when digital information is distributed in encoded form,it may be desirable to allow unauthorized users to play the informationwith a digital player, perhaps with a reduced level of quality. Forexample, a popular song may be encoded and freely distributed in encodedform to the public. The public, perhaps using commonly available plug-indigital players, could play the encoded content and hear the music insome degraded form. The music may-sound choppy, or fuzzy or be degradedin some other way. This lets the public decide, based on the availablelower quality version of the song, if they want to purchase a key fromthe publisher to decode, or “clean-up,” the content. Similar approachescould be used to distribute blurry pictures or low quality video. Oreven “degraded” text, in the sense that only authenticated portions ofthe text can be determined with the predetermined key or a validateddigital signature for the intended message.

In view of the foregoing, it can be appreciated that a substantial needexists for a method allowing encoded content to be played, with degradedquality, by a plug-in digital player, and solving the other problemsdiscussed above.

SUMMARY OF THE INVENTION

The disadvantages of the art are alleviated to a great extent by amethod for combining transfer functions with predetermined key creation.In one embodiment, digital information, including a digital sample andformat information, is protected by identifying and encoding a portionof the format information. Encoded digital information, including thedigital sample and the encoded format information, is generated toprotect the original digital information.

In another embodiment, a digital signal, including digital samples in afile format having an inherent granularity, is protected by creating apredetermined key. The predetermined key is comprised of a transferfunction-based mask set to manipulate data at the inherent granularityof the file format of the underlying digitized samples.

With these and other advantages and features of the invention that willbecome hereinafter apparent, the nature of the invention may be moreclearly understood by reference to the following detailed description ofthe invention, the appended claims and to the several drawings attachedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block flow diagram of a method for copy protection orauthentication of digital information according to an embodiment of thepresent invention.

DETAILED DESCRIPTION

In accordance with an embodiment of the present invention, a methodcombines transfer functions with predetermined key creation. Increasedsecurity is achieved in the method by combining elements of “public-keysteganography” with cryptographic protocols, which keep in-transit datasecure by scrambling the data with “keys” in a manner that is notapparent to those with access to the content to be distributed. Becausedifferent forms of randomness are combined to offer robust, distributedsecurity, the present invention addresses an architectural “gray space”between two important areas of security: digital watermarks, a subset ofthe more general art of steganography, and cryptography. One form ofrandomness exists in the mask sets that are randomly created to mapwatermark data into an otherwise unrelated digital signal. The secondform of randomness is the random permutations of data formats used withdigital players to manipulate the content with the predetermined keys.These forms can be thought of as the transfer function versus themapping function inherent to digital watermarking processes.

According to an embodiment of the present invention, a predetermined, orrandomly generated, key is used to scramble digital information in a waythat is unlike known “digital watermark” techniques and public keycrypto-systems. As used herein, a key is also referred to as a “maskset” which includes one or more random or pseudo-random series of bits.Prior to encoding, a mask can be generated by any cryptographicallysecure random generation process. A block cipher, such as a DataEncryption Standard (DES) algorithm, in combination with a sufficientlyrandom seed value, such as one created using a Message Digest 5 (MD5)algorithm, emulates a cryptographically secure random bit generator. Thekeys are saved in a database, along with information matching them tothe digital signal, for use in descrambling and subsequent viewing orplayback. Additional file format or transfer property information isprepared and made available to the encoder, in a bit addressable manner.As well, any authenticating function can be combined, such as DigitalSignature Standard (DSS) or Secure Hash Algorithm (SHA).

Using the predetermined key comprised of a transfer function-based maskset, the data representing the original content is manipulated at theinherent granularity of the file format of the underlying digitizedsamples. Instead of providing, or otherwise distributing, watermarkedcontent that is not noticeably altered, a partially “scrambled” copy ofthe content is distributed. The key is necessary both to register thesought-after content and to descramble the content into its originalform.

The present invention uses methods disclosed in “Method for Stega-CipherProtection of Computer Code,” U.S. patent application Ser. No.08/587,943 (issued as U.S. Pat. No. 5,745,569 on Apr. 28, 1998), withrespect to transfer functions related to the common file formats, suchas PICT, TIFF, AIFF, WAV, etc. Additionally, in cases where the contenthas not been altered beyond being encoded with such functional data, itis possible for a digital player to still play the content because thefile format has not been altered. Thus, the encoded content could stillbe played by a plug-in digital player as discrete, digitally sampledsignals, watermarked or not. That is, the structure of the file canremain basically unchanged by the watermarking process, letting commonfile format based players work with the “scrambled” content.

For example, the Compact Disc-Digital Audio (CD-DA) format stores audioinformation as a series of frames. Each frame contains a number ofdigital samples representing, for example, music, and a header thatcontains file format information. As shown in FIG. 1, according to anembodiment of the present invention some of the header information canbe identified and “scrambled” using the predetermined key at steps 110to 130. The music samples can remain unchanged. Using this technique, atraditional CD-DA player will be able to play a distorted version of themusic in the sample. The amount of distortion will depend on the way,and extent, that the header, or file format, information has beenscrambled. It would also be possible to instead scramble some of thedigital samples while leaving the header information alone. In general,the digital signal would be protected by manipulating data at theinherent granularity, or “frames,” of the CD-DA file format. To decodethe information, a predetermined key is used before playing the digitalinformation at steps 140 and 150.

A key-based decoder can act as a “plug-in” digital player of broadcastsignal streams without foreknowledge of the encoded media stream.Moreover, the data format orientation is used to partially scramble datain transit to prevent unauthorized descrambled access by decoders thatlack authorized keys. A distributed key can be used to unscramble thescrambled content because a decoder would understand how to process thekey. Similar to on-the-fly decryption operations, the benefits inherentin this embodiment include the fact that the combination of watermarkedcontent security, which is key-based, and the descrambling of the data,can be performed by the same key which can be a plurality of mask sets.The mask sets may include primary, convolution and message delimitermasks with file format data included.

The creation of an optimized “envelope” for insertion of watermarksprovides the basis of much watermark security, but is also acomplementary goal of the present invention. The predetermined or randomkey that is generated is not only an essential map to access the hiddeninformation signal, but is also the descrambler of the previouslyscrambled signal's format for playback or viewing.

In a system requiring keys for watermarking content and validating thedistribution of the content, different keys may be used to encodedifferent information while secure one way hash functions or one-timepads may be incorporated to secure the embedded signal. The same keyscan be used to later validate the embedded digital signature, or evenfully decode the digital watermark if desired. Publishers can easilystipulate that content not only be digitally watermarked but thatdistributors must check the validity of the watermarks by performingdigital signature-checks with keys that lack any other functionality.The system can extend to simple authentication of text in otherembodiments.

Before such a market is economically feasible, there are other methodsfor deploying key-based watermarking coupled with transfer functions topartially scramble the content to be distributed without performing fullpublic key encryption, i.e., a key pair is not necessarily generated,simply, a predetermined key's function is created to re-map the data ofthe content file in a lossless process. Moreover, the scramblingperformed by the present invention may be more dependent on the file inquestion. Dissimilarly, encryption is not specific to any particularmedia but is performed on data. The file format remains unchanged,rendering the file useable by any conventional viewer/player, but thesignal quality can be intentionally degraded in the absence of theproper player and key. Public-key encryption seeks to completely obscurethe sensitive “plaintext” to prevent comparisons with the “ciphertext”to determine a user's private keys. Centralized encryption only differsin the utilization of a single key for both encryption and decryptionmaking the key even more highly vulnerable to attacks to defeat theencryption process. With the present invention, a highly sought afterphotograph may be hazy to the viewer using any number of commonlyavailable, nonproprietary software or hardware, without the authorizedkey. Similarly, a commercially valuable song may sound poor.

The benefit of some form of cryptography is not lost in the presentinvention. In fact, some piracy can be deterred when the target signalmay be known but is clearly being protected through scrambling. What isnot anticipated by known techniques, is an ala carte method to changevarious aspects of file formatting to enable various “scrambled states”for content to be subsequently distributed. An image may lack all redpixels or may not have any of the most significant bits activated. Anaudio sample can similarly be scrambled to render itless-than-commercially viable.

The present invention also provides improvements over knownnetwork-based methods, such as those used for the streaming of mediadata over the Internet. By manipulating file formats, the broadcastmedia, which has been altered to “fit” within electronic distributionparameters, such as bandwidth availability and error correctionconsiderations, can be more effectively utilized to restrict thesubsequent use of the content while in transit as well as real-timeviewing or playing.

The mask set providing the transfer function can be read on a per-usebasis by issuing an authorized or authenticating “key” for descramblingthe signal that is apparent to a viewer or a player or possessor of theauthenticating key. The mask set can be read on a per-computer basis byissuing the authorized key that is more generalized for the computerthat receives the broadcast signals. Metering and subscription modelsbecome viable advantages over known digital watermark systems whichassist in designating the ownership of a copy of digitized mediacontent, but do not prevent or restrict the copying or manipulation ofthe sampled signal in question. For broadcast or streamed media, this isespecially the case. Message authentication is also possible, though notguaranteeing the same security as an encrypted file as with generalcrypto systems.

The present invention thus benefits from the proprietary player modelwithout relying on proprietary players. No new players will be necessaryand existing multimedia file formats can be altered to exact a measureof security which is further increased when coupled with digitalwatermarks. As with most consumer markets for media content, predominantfile formats exist, de facto, and corresponding formats for computerslikewise exist. For a commercial compact disc quality audio recording,or 16 bit 44.1 kHz, corresponding file formats include: AudioInterchange File Format (AIFF), Microsoft WAV, Sound Designer II, Sun's.au, Apple's Quicktime, etc. For still image media, formats aresimilarly abundant: TIFF, PICT, JPEG, GIF, etc. Requiring the use ofadditional proprietary players, and their complementary file formats,for limited benefits in security is wasteful. Moreover, almost allcomputers today are multimedia-capable, and this is increasingly so withthe popularity of Intel's MMX chip architecture and the PowerPC line ofmicrochips. Because file formatting is fundamental in the playback ofthe underlying data, the predetermined key can act both as a map, forinformation to be encoded as watermark data regarding ownership, and adescrambler of the file that has been distributed. Limitations will onlyexist in how large the key must be retrofitted for a given application,but any manipulation of file format information is not likely to exceedthe size of data required versus that for an entire proprietary player.

As with previous disclosures by the inventor on digital watermarkingtechniques, the present invention may be implemented with a variety ofcryptographic protocols to increase both confidence and security in theunderlying system. A predetermined key is described as a set of masks.These masks may include primary, convolution and message delimiter mask.In previous disclosures, the functionality of these masks is definedsolely for mapping. The present invention includes a mask set which isalso controlled by the distributing party of a copy of a given mediasignal. This mask set is a transfer function which is limited only bythe parameters of the file format in question. To increase theuniqueness or security of each key used to scramble a given media filecopy, a secure one way hash function can be used subsequent to transferproperties that are initiated to prevent the forging of a particularkey. Public and private keys may be used as key pairs to furtherincrease the unlikeliness that a key may be compromised.

These same cryptographic protocols can be combined with the embodimentsof the present invention in administering streamed content that requiresauthorized keys to correctly display or play the streamed content in anunscrambled manner. As with digital watermarking, synunetric orasymmetric public key pairs may be used in a variety of implementations.Additionally, the need for certification authorities to maintainauthentic key-pairs becomes a consideration for greater security beyondsymmetric key implementations. The cryptographic protocols makespossible, as well, a message of text to be authenticated by a messageauthenticating function in a general computing device that is able toensure secure message exchanges between authorizing parties.

Although various embodiments are specifically illustrated and describedherein, it will be appreciated that modifications and variations of thepresent invention are covered by the above teachings and within thepurview of the appended claims without departing from the spirit andintended scope of the invention. Other embodiments and uses of theinvention will be apparent to those skilled in the art fromconsideration of the specification and practice of the inventiondisclosed herein. The specification and examples should be consideredexemplary only with the true scope and spirit of the invention indicatedby the following claims. As will be easily understood by those ofordinary skill in the art, variations and modifications of each of thedisclosed embodiments can be easily made within the scope of thisinvention as defined by the following claims.

1-5. (canceled)
 6. A method for protecting a digital signal, comprisingthe steps of: providing a digital signal comprising digital data andfile format information defining how the digital signal is encoded;creating a predetermined key to manipulate the digital signal; andmanipulating the digital signal using the predetermined key to generateat least one permutation of the digital signal parameterized by the fileformat information defining how the digital signal is encoded.
 7. Themethod of claim 6, wherein the digital signal represents a continuousanalog waveform.
 8. (canceled)
 9. The method of claim 6, wherein thedigital signal is a message to be authenticated.
 10. (canceled)
 11. Themethod of claim 6, further comprising the step of: using a digitalwatermarking technique to encode information that identifies ownership,use, or other information about the digital signal, into the digitalsignal.
 12. The method of claim 6, wherein the digital signal representsa still image, audio or video.
 13. The method of claim 6, wherein thepredetermined key comprises one or more mask sets having random orpseudo-random series of bits, the method further comprising the step of:validating the one or more mask sets before manipulating the file formatinformation using the predetermined key.
 14. The method of claim 6,wherein the predetermined key comprises one or more mask sets havingrandom or pseudo-random series of bits, the method further comprisingthe step of: validating the one or more mask sets after manipulating thefile format information using the predetermined key. 15.-17. (canceled)18. The method of claim 13, further comprising the step of: using adigital watermarking technique to embed information that identifiesownership, use, or other information about the digital signal, into thedigital signal; and wherein said step of validating is dependent onvalidation of the embedded information.
 19. (canceled)
 20. A method forprotecting a digital signal, comprising the steps of: providing adigital signal comprising digital data and file format informationdescribing how the digital signal is encoded; creating a predeterminedkey comprising a mask set; manipulating the digital signal using thepredetermined key wherein the manipulation is parameterized by the fileformat information describing how the digital signal is encoded;authenticating the predetermined key during playback of the digitaldata; and metering the playback of the digital data to monitor content.21. The method of claim 20, wherein the predetermined key isauthenticated to authenticate message information. 22-29. (canceled) 30.A method for protecting digital data, where the digital data isorganized into a plurality of frames, each frame having i) a headercomprising file format information and ii) at least a portion of thedigital data, said method comprising the steps of: creating apredetermined key to manipulate the file format information in one ormore of the plurality of frames wherein the file format informationdefines how the digital data is encoded; and manipulating the fileformat information using the predetermined key in at least two of theplurality of frames wherein the file format information defines how thedigital data is encoded, such that the digital data will be perceived bya human as noticeably altered if it is played without using a decode keyto restore the file format information to a prior state.
 31. (canceled)32. A system for scrambling a digital signal comprising: a receiver forreceiving a digital signal comprising digital data and file formatinformation defining how the digital signal is encoded; a key generatorfor generating a predetermined key to manipulate the digital signal; anda scrambler for manipulating the digital signal using the predeterminedkey to generate at least one permutation of the digital signalparameterized by the file format information defining how the digitalsignal is encoded.
 33. The system of claim 32, wherein the digitalsignal represents a continuous analog waveform.
 34. The system of claim32, wherein the digital signal is a message to be authenticated.
 35. Thesystem of claim 32, further comprising an encoder for using a digitalwatermarking technique to encode information that identifies ownership,use, or other information about the digital signal, into the digitalsignal.
 36. The system of claim 32, wherein the digital signalrepresents a still image, audio or video.
 37. The system of claim 32,wherein the predetermined key comprises a plurality of mask sets. 38.The system of claim 32, wherein the predetermined key comprises a keypair comprising a public key and a private key.